The present invention relates to an ultrasound probe and a method of producing the same and in particular to an ultrasound probe comprising a plurality of inorganic piezoelectric elements and a plurality of organic piezoelectric elements layered on each other and a method of producing the same.
Conventionally, ultrasound diagnostic apparatus using ultrasound images are employed in medicine. Generally, an ultrasound diagnostic apparatus of this type transmits an ultrasonic beam from an ultrasound probe into a subject, receives an ultrasound echo from the subject with the ultrasound probe, and electrically processes the resulting reception signals to produce an ultrasound image.
In recent years, attention is paid to harmonic imaging whereby a harmonic component, which is generated as ultrasonic waveforms deform due to non-linearity of the subject, is received and visualized to give more accurate diagnosis.
JP 11-155863 A, for example, proposes an example as an ultrasound probe appropriate for use in harmonic imaging comprising inorganic piezoelectric elements each using an inorganic piezoelectric body made of a material such as lead zirconate titanate (PZT) and organic piezoelectric elements each using an organic piezoelectric body made of a material such as polyvinylidene fluoride (PVDF), such that the inorganic piezoelectric elements and the organic piezoelectric elements are layered over each other.
The inorganic piezoelectric elements can transmit a higher output ultrasonic beam, and organic piezoelectric elements can receive a harmonic signal with high sensitivity.
The inorganic piezoelectric elements and the organic piezoelectric elements are layered on each other through the intermediary of an acoustic matching layer for efficient transmission of ultrasonic waves. Conventionally, the acoustic matching layer is severed into a plurality of pieces corresponding to a plurality of inorganic piezoelectric elements so that the organic piezoelectric elements are disposed on the respective severed acoustic matching layers. Thus, the inorganic piezoelectric elements and the organic piezoelectric elements are provided in the same number of channels and at the same pitch. With such configuration, grating lobes are liable to occur as the organic piezoelectric elements receive a high-order harmonic component, possibly resulting in a lower image quality.
Each organic piezoelectric element has a signal electrode layer connected to a surface of the corresponding organic piezoelectric body. A signal line extension electrode extended from the signal electrode layer is connected by, for example, welding to a wiring pattern provided on a circuit board constituting a reception circuit. The reception signal obtained by the organic piezoelectric element is acquired by the reception circuit via the signal line extension electrode.
However, an organic piezoelectric body generally has such a low heat resistance that it depolarizes at a temperature over 80° C. Therefore, it has been a problem that remains to be solved to reduce the amount of heat conducted to the organic piezoelectric body via the signal line extension electrode generated when the signal line extension electrode is connected by, for example, welding to the wiring pattern provided on the circuit board. The problem has been especially important when a large number of organic piezoelectric elements are arrayed in a compact space.